Variable h-guide directional coupler



March 23, 1965 J. RElNm-:L l VARIABLE H--GUIDE DIRECTIONAI.. COUPLER Filed Aug. 29, '1965 ON m 223m 2 3 SEEE# www ` ATTOR N EY United States Patent Oiiiice 3,115,171 Patented Mar. 23, 1965 3,175,171 VARIABLE H-GUIDE DIRECTIONAL COUPLER John Reindel, San Diego, Calif., assigner to Sylvania Electric Products Inc., a corporation of Delaware Filed Aug. 29, 1963, Ser. No. 305,377 2 Claims. (Cl. S33-10) This invention relates to directional couplers, and more particularly to a variable waveguide directional coupler.

The paths of current iiowing in rectangular waveguide propagating the dominant or TEN) mode place serious limitations on the eiciency of variable directional coupling between adjacent waveguides. Such variable coupling is generally accomplished with a conducting plate which is movable relative to interguide coupling apertures in a wall common to the waveguides as described in Patent No. 2,735,069. Disc'oritinuities in the transverse and longitudinal current flow caused by imperfect electrical contact between the plate and the common waveguide wall produce secondary waves in the waveguides which adversely affect the directivity and eiiiciency of the coupling.

In accordance with this invention, coupling takes place between contiguous H-plane waveguides which have a common wall. Part of the common wall comprises a plate formed with coupling apertures and movable in the plane of the common wall in a direction transverse to the direction of wave propagation. This coupler may be connected to standard rectangular waveguides through wave transducers which provide transition between the wave modes of the H-plane and standard waveguides. Coupling between the contiguous waveguide sections decreases as the movable plate displaces the apertures farther away from the mid-plane of the contiguous sections. Since current in the H-plane waveguide does not flow longitudinally, discontinuities at the junction of the plate and stationary part of the common wall have no affect on coupling efficiency.

An object of this invention is the provision of a variable waveguide directional coupler which is not atected by electrical discontinuities at the junction 'of movable and stationary parts of the coupler.

Another object is the provision of a variable directional coupler of convenient size for operation at high frequencies.

A further object is the provision of a variable directional coupler which may be readily modied to provide different coupling characteristics by interchanging movable coupling plates.

Another object is the provision of a variable directional coupler with an open construction.

These and other objects of the invention will be more fully understood from the following description of a preferred embodiment thereof reference being had to the accompanying drawing which is a perspective view, partially broken away, of a variable H-plane waveguide coupler.

Referring to the drawing, the coupler comprises a pair of contiguous H-plane waveguides 1 and 2, transducer sections 3 and 4 connected to opposite ends of waveguide 1, transducer section 5 connected to 'one end of waveguide 2 and a termination element 6 connected to the other end of waveguide 2. The transducer sections 3, 4 and 5 connect to closed rectangular waveguides 7, 8 and 9, respectively, having flanges 7, 8 and 9'.

H-plane waveguide 1 has laterally spaced parallel broad walls 11 and 12 and is open along the outer edges of those walls as indicated at 13 and 14. A slab 15 of dielectric material is secured to walls 11 and 12 midway between their outer edges and extends longitudinally of the waveguide for a substantial portion of its length.

Waveguide 2 is similarly constructed with parallel walls 17 and 18, open outer edges, and a dielectric slab (not shown) connecting the mid-portions of the walls.

The H-plane waveguide is more fully described in an article entitled The H-Guide, A Waveguide For Microwaves by F. l. Tischer published in IRE Convention Record, 1956, Microwave and Instruments, Part 5, page 44, and does not per se constitute this invention.

Adjacent walls 12 and 17 of the two H-plane waveguides 1 and 2 merge to form a common plane wall comprising a stationary portion 2t) and a plate 21 supported at its edges 21a and 2lb on the stationary portion for sliding movement in the plane of the wall transversely of the direction of wave propagation in the guide. The dimension L of plate 21 in the direction of its movement is substantially greater than the width W of the H-guide walls 11, 18 and 20. Each dielectric slab 1S is secured to stationary wall portions Zd and extends longitudinally of and abuts plate 21 so as to permit movement of the plate relative to the slab.

The mid portion of plate 21 is formed with one or more coupling apertures, illustrated in the drawings as an array of circular openings 23 spaced apart in the direction of propagation. These apertures may vary in number, size, shape and construction depending upon the nature and degree of coupling desired, and provide the means for coupling electromagnetic wave energy from H-guide 1 into H-guide 2. The transverse location of apertures 23 relative to guide walls 11, 18 and 20, that is, the Spacing of apertures 23 from open edges 13 and 14 of the guides, is varied by transverse movement of plate 21. The amount of energy transferred between the H- guides is directly related to the transverse location of the coupling apertures, and therefore selective movement of plate 21 produces a desired variation in this coupled energy.

Transducers 3, 4 and 5 are substantially identical, and each comprises diverging walls 25 which connect the broad walls of the associated waveguides 7, 8 or 9 to the outer open edges 'of the H-guide. Parallel walls 26 of each transducer connect the narrow walls of the associated waveguide to respective broad walls of the H- guide. These transducers change the mode of the propagating electromagnetic waves between the TEM, mode, for example, in waveguides 7, 8 and 9* and the HE mode in H-guides 1 and 2.

The field distribution in H-guides 1 and 2 is such that the greater part 'of the energy transmitted through them is located at or adjacent to the dielectric slabs 15, and the fields decay exponentially toward the open edges 13 and 14 of the guides. Therefore, maximum coupling between guides 1 and 2 occurs when apertures are located at or adjacent to slabs 1S, and is decreased when plate 21 is moved so as to displace the apertures in either direction toward the outer edges of the guides.

In the embodiment shown in the drawing, electromagnetic wave energy is fed by waveguide 7 through transducer 3 into H-guide 1. A portion of this input energy is coupled through apertures 23)` into H-guide 2, the magnitude of the coupled energy depending upon the transverse location of the apertures. The remainder of the input energy passes through transducer 4 into waveguide 8 in which the waves propagate in their original mode. Substantially all of the energy coupled into H-guide 2 passes through transducer S and into waveguide 9, and any energy propagating in the opposite direction in H-guide 2 is absorbed by termination element 6.

The characteristic current flow in the walls of H-guides 1 and 2 is such that there are no longitudinal currents. Therefore the junction of plate edge 21a or 2lb with the stationary wall part 20 is not critical since currents do not traverse these connections and no secondary waves are produced by such discontinuities in the guide wall. The physical dimensions of H-guide are substantially greater than closed rectangular waveguide, and this property together with the open construction of the guide facilitates fabrication and operation of the directional coupler at frequencies in X-band and K-band regions.

What is claimed is: 1. A directional coupler for electromagnetic wave energy comprising iirst and second contiguous H-guides having outer walls and an intermediate plane common wall parallel to said outer walls, each of said guides having open outer edges and a dielectric slab extending between the outer and common walls midway between said outer edges, said common wall comprising a stationary portion and a plate supported on the stationary portion for movement in the plane thereof, said plate having a dimension in the direction of its movement greater than the corresponding dimensions of said outer walls and said stationary common wall portion and having a plurality of apertures formed therein for coupling energy from the first guide to the second guide, the location of said apertures relative to said outer walls and said stationary common wall portion being variable by said movement of said plate whereby to change the magnitude of energy coupled from the first to the second guide, Y input and rst and second output waveguides adapted to propagate electromagnetic waves in the dominant mode, l first and second transducers connecting said input and first output waveguides, respectively, to opposite ends of said first Haguide, a third transducer connecting said second output waveguide to the end of said second lel-guide remote fromy the input waveguide connection to the first H-guide,

each of said transducers providing a transition of electromagnetic waves between the dominant mode in the waveguide and the HEH mode in the -I-guide, and

terminating means at the end of said second H-guide opposite from the third waveguide for absorbing reverseiy propagating energy. Y

2. A directional coupler for electromagnetic wave energy comprising Iirst and second contiguous H-guides having Vouter walls and an intermediate plane common wall parallel to said outer Walls,

each of said guides having open outer edges and a dielectric slab extending between the outer and common walls midway betwen said outer edges,

said common wall comprising a stationary portion and a plate supported on the stationary portion for movement in the plane thereof, t

said plate having a dimension in the direction of its movement greater than the corresponding dimensions of said outer walls and said stationary common wall portion and having a plurality of longitudinally spaced apertures formed centrally therein for coupling energy from the first guide to the second guide, the location of said apertures relative to said outer walls and said stationary common wall portion being variable by said movement of said plate whereby to change the magnitude of energy coupled from the irst to the second guide,

means for propagating microwave energy in one direction through said rst l-I-guide, and t terminating means at the end of said second H-guide opposite from the direction of waves propagation in the Hguide for absorbing energy.

References Cited by the Examiner UNITED STATES PATENTS 2,829,347 4/58 Tomiyasu 333-7 OTHER REFERENCES Tischer: H-Guide-A New Microwave Concept,

Electronic'lndustrial Tele-Tech., 1956, 15, page 50.

ELI LIEBERMAN, Acting Primary Examiner'.

HERMAN KARL SAALBACH, Examiner. 

1. A DIRECTIONAL COUPLER FOR ELECTROMAGNETIC WAVE ENERGY COMPRISING FIRST AND SECOND CONTIGUOUS H-GUIDES HAVING OUTER WALLS AND AN INTERMEDIATE PLANE COMMON WALL PARALLEL TO SAID OUTER WALLS, EACH OF SAID GUIDES HAVING OPEN OUTER EDGES AND A DIELECTRIC SLAB EXTENDING BETWEEN THE OUTER AND COMMON WALLS MIDWAY BETWEEN SAID OUTER EDGES, SAID COMMON WALL COMPRISING A STATIONARY PORTION AND A PLATE SUPPORTED ON THE STATIONARY PORTION FOR MOVEMENT IN THE PLANE THEREOF, SAID PLATE HAVING A DIMENSION IN THE DIRECTION OF ITS MOVEMENT GREATER THAN THE CORRESPONDING DIMENSIONS OF SAID OUTER WALLS AND SAID STATIONARY COMMON WALL PORTION AND HAVING A PLURALITY OF APERTURES FORMED THEREIN FOR COUPLING ENERGY FROM THE FIRST GUIDE TO THE SECOND GUIDE, THE LOCATION OF SAID APERTURES RELATIVE TO SAID OUTER WALLS AND SAID STATIONARY COMMON WALL PORTION BEING VARIABLE BY SAID MOVEMENT OF SAID PLATE WHEREBY TO CHANGE THE MAGNITUDE OF ENERGY COUPLED FROM THE FIRST TO THE SECOND GUIDE, INPUT AND FIRST AND SECOND OUTPUT WAVEGUIDES ADAPTED TO PROPAGATE ELECTROMAGNETIC WAVES IN THE DOMINANT MODE, FIRST AND SECOND TRANSDUCERS CONNECTING SAID INPUT AND FIRST OUTPUT WAVEGUIDES, RESPECTIVELY, TO OPPOSITE ENDS OF SAID FIRST H-GUIDE, A THIRD TRANSDUCER CONNECTING SAID SECOND OUTPUT WAVEGUIDE TO THE END OF SAID SECOND H-GUIDE REMOTE FROM THE INPUT WAVEGUIDE CONNECTION TO THE FIRST H-GUIDE EACH OF SAID TRANSDUCERS PROVIDING A TRANSITION OF ELECTROMAGNETIC WAVES BETWEEN THE DOMINANT MODE IN THE WAVEGUIDE AND THE HE11 MODE IN THE H-GUIDE, AND TERMINATING MEANS AT THE END OF SAID SECOND H-GUIDE OPPOSITE FROM THE THIRD WAVEGUIDE FOR ABSORBING REVERSELY PROPAGATING ENERGY. 